these are both wholesale (do you know anyone with a resale badge?) but if you call, ask if they will sell retail (it's probably a 40% mark-up) - also ask if they are open to the Public (after 10 am, weekdays)
Entrance to parking is on 6th Street near Brannan Street - but before 10 am you will need a Flower Market badge -
Floral Supply Syndicate
670 Brannan Street
Shibata Floral Company
415.543.9880 or 495.8611
620 Brannan Street
retail will probably be in the $13 range per item, depending on size
pix #1 is at Shibata
pix #2 is at Floral Supply
I've seen them at Pottery Barn, but they make them look like they're for holding flowers or other items.
You may want to try Economy Restaurant Fixtures, who are having a sale this weekend, but if you did find them you may have to buy them by the case (about 12 per but it varies). But this will fairly cheap. I recently bought a bunch of glassware here for a large party because it's cheaper than renting.
Also try Cookin' on Divis and the junk/antique shop next to it. I found some very nice cocktail glasses there recently. I see julep cups all the time in junk shops but usually as singles and marketed as a baby cup.
Economy Restaurant Fixtures
1200 7th St, San Francisco, CA
339 Divisadero St, San Francisco, CA